System for applying a wood veneer across a corner of an elongate core

ABSTRACT

A method of veneering across a elongate corner on an elongate core involving providing a sheet of veneer sized to cover a desired portion of the core including an expanse on each side of the corner with the veneer having a core side for placement against the core and an exposed side opposite the core side. An elongate groove is formed in the core side of the veneer with the groove having a generally triangular cross-section with an open side substantially coplanar with the core side of the veneer and two interior sides extending into the veneer to a point near but not reaching the exposed side of the veneer where the angle between the interior sides being configured to match the angle of the corner. Lastly the veneer is applied to the core with the groove aligned over the corner and veneer on either side of the groove folded down against the core to thereby bring the two interior sides of the groove together.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation of U.S. patent applicationSer. No. 09/189,917 filed Nov. 10, 1998 which application is acontinuation of U.S. patent application Ser. No. 08/799,579 filed Feb.12, 1997.

FIELD OF THE INVENTION

[0002] The present invention relates to applying wood veneer to a core,and more particularly to applying a single piece of veneer over a sharpcorner on a core.

BACKGROUND

[0003] Recent environmental regulations and approaching exhaustion ofold-growth timber supplies have made it increasingly difficult andexpensive for manufacturers to obtain high-grade lumber to use in theirwood products. Such products include furniture, cabinets and millwork.This is particularly a problem for products which are stained ratherthan painted because the stain does not cover any underlyingirregularities in the wood. With painted products, on the other hand,many of the defects in the wood are covered by the finish.

[0004] One way of addressing the shortage and high cost of high qualitylumber is use of veneered stock. Typically, veneered parts are createdby laminating a high quality, i.e., clear, veneer over a lower gradecore material, such as medium density fiberboard (MDF), particle board,plywood or finger-jointed stock. Use of veneered parts results in asubstantially more efficient utilization of high quality wood, andtherefore reduces raw material costs. Unfortunately, the actual processof applying the veneer can be relatively complex.

[0005] Veneering is relatively simple if only a single flat surface ortwo opposed flat surfaces, i.e., one or two sides of a piece of plywood,must be covered. However, covering adjacent sides of a core issubstantially more difficult. In particular, multiple processing stepsare required to cover adjacent sides. In a first step, the veneer isapplied to one of the adjacent sides. The other side of the partiallyveneered piece must then be surfaced or milled to remove excess glue oroverhang of the first applied piece of veneer. After the milling step,the second piece of veneer can be applied. Lastly, the edges of thesecond piece of veneer must be milled. Thus, applying veneers to two ormore adjacent surfaces is a time-consuming and costly process.

[0006] Another difficulty incumbent in applying a veneer to two adjacentsides simultaneously is supplying sufficient heat to quickly cure thethermosetting adhesive that is often used for veneering. In particular,at least with thicker veneers, simple conduction heating from heatedplatens is relatively slow and creates a significant bottleneck inmaterial processing. Radio frequency (RF) heating, on the other hand,heats at a rate that is substantially independent of the thickness ofthe veneer. Unfortunately, heating two perpendicularly oriented gluelines using RF techniques is difficult because of the preferentialheating of glue lines oriented parallel to the electric field. Thepreferential heating is believed to lead to excess heating of theparallel glue line prior to achieving adequate heating of theperpendicular line.

[0007] It is therefore an object of the present invention to provide asystem for applying a veneer on two or more adjacent sides of a core ina single step.

[0008] It is another object of the present invention to provide a systemof veneering that eliminates the need to resurface the core betweenveneering steps.

[0009] One more object of the present invention is to provide a systemfor veneering that results in a visually attractive corner.

[0010] Another object is to provide a system of veneering that isflexible enough to accommodate an edge band with the veneer in a singlestep.

[0011] Yet another object of the present invention is to provide asystem for pressing and heating a veneered article.

[0012] It is also an object of the present invention to provide a systemfor pressing and heating a veneered article that can heat orthogonalglue lines in a single step.

SUMMARY OF THE INVENTION

[0013] The present invention is a method of veneering across an elongatecorner on an elongate core. The method involves providing a sheet ofveneer sized to cover a desired portion of the core including an expanseon each side of the corner with the veneer having a core side forplacement against the core and an exposed side opposite the core side.An elongate groove is formed in the core side of the veneer with thegroove having a generally triangular cross-section with an open sidesubstantially coplanar with the core side of the veneer and two interiorsides extending into the veneer to a point near but not reaching theexposed side of the veneer where the angle between the interior sidesbeing configured to match the angle of the corner. Lastly the veneer isapplied to the core with the groove aligned over the corner and veneeron either side of the groove folded down against the core to therebybring the two interior sides of the groove together.

[0014] The present invention also includes a press configured to supplypressure to adjacent sides of a press charge simultaneously. The pressis also configured to heat adjacent sides of a press charge using radiofrequency heating.

BRIEF DESCRIPTION OF THE FIGURES

[0015]FIG. 1 shows a veneer sheet prepared according to the presentinvention.

[0016]FIG. 2 shows a sectional view through a groove in a veneer sheetprepared according to the present invention.

[0017]FIG. 3 shows a veneered article according to the presentinvention.

[0018]FIG. 4 shows a perspective view of a press constructed accordingto the present invention.

[0019]FIG. 5 is a cross-sectional view through the press of FIG. 4 alongline 5-5.

[0020]FIG. 6 shows a window utilizing an extension jamb preparedaccording to the present invention.

DETAILED DESCRIPTION AND BEST MODE OF CARRYING OUT THE INVENTION

[0021] A sheet of veneer prepared for use according to the presentinvention is shown generally at 10 in FIG. 1. In an embodiment forcovering four sides of a core, sheet 10 includes three longitudinallyextending grooves 12 a-c. Each groove is triangular in cross-sectionwith an open side 14 and two interior sides 16 which extendsubstantially all the way through the veneer to a point 18, as shown inFIG. 2. The angle between the interior sides is determined by the anglethrough which the veneer must fold when applied. The sheet also includestwo beveled lateral edges 20 a-b. The grooves and bevels are preferablyformed with a V-grooving machine, such as an Auto ‘V’ grooving, Inc.,AVG-48-HSFWPL universal V-groover, although a table saw can be used aswell by tilting the blade 45-degrees.

[0022] A hinge structure is formed on the sheet under the point of thegroove, as shown in FIG. 2, to aid in preventing cracking or separatingwhen the veneer is folded. In the preferred embodiment, the hingestructure takes the form of a layer of hot melt glue 22, such asJowatherm EP 613121 Antislip hotmelt glue by Jowat Corporation. The gluemay be applied by rolling the sheet over a roller partially submerged ina bath of melted glue. It may be desirable to reinforce the glue byembedding fibers, such as small polyester or glass fibers, in glueacross the joint. It should be understood that tape may be used as well,if desired, or paper or fleece could be applied over the hot melt glueto provide extra strength. The hinge structure may also take the form ofstitches spanning the groove. The stitches may be formed by a machineknown as a stitcher or veneer splicer, which is used to stitch veneersheets together.

[0023] In FIG. 2 it can be seen that, in the preferred embodiment, thegroove does not completely sever the veneer, but rather leaves a thinlayer of wood at the point of the groove which forms part of the hingestructure. The thin layer of wood is useful because it holds the sheetof veneer together after the grooves are cut if the glue or tape is tobe applied at a later time.

[0024] Sheet 10 is sized and the grooves are spaced for applicationaround a core 24 to form a veneered article, as shown in FIG. 3. Core 24includes four sharp corners 26 a-d separating four surface expanses orregions 28 a-d. It will be understood by those of skill in the art thatcore 24 is preferably a lower grade product than sheet 10. For instance,core 24 could be formed from MDF, finger-jointed stock or other low costmaterial, while sheet 10 is preferably formed from clear, defect freewood. Most commonly, core 24 will be relatively elongate with the grainof the veneer running parallel to the elongate axis. It is also possiblehowever, to orient the veneer in the opposite direction so that thegrooves run across the grain, or in other directions.

[0025] As shown in FIG. 3, sheet 10 fits closely about core 24 with thegrooves disposed over the sharp corners. The spacing between the groovesis set to correspond to the distance between the sharp corners so thatno gaps are left when the veneer is applied. Likewise, the angle betweenthe internal sides of the grooves is chosen to match the angle of thesharp corner over which the groove is to be disposed. For instance,groove 12 a has a 90-degree angle and fits over a 90-degree sharpcorner, i.e., corner 26 a, on the core. Groove 12 b, in contrast, has anangle of only 60-degrees because veneer only needs to fold 60-degreesover sharp corner 26 b. Although the sheet is shown with bevels 20 a-b,it is also possible to simply butt the edges of the veneer together atsharp edge 26 d, rather than forming a beveled corner and therebyeliminating the edge bevels.

[0026] The veneer is preferably glued onto the core with a thermosettingresin. As will be described below, the resin is heated in a press whichsupplies both heat and pressure to the veneered article. Because theveneer is relatively thick, conduction heating of the veneer isrelatively slow. Therefore, RF heating is used in the preferredembodiment. There are many possibilities for the type of glue, but apolyvinyl acetate (PVA) glue is used in the preferred embodiment becauseof its suitability for RF heating.

[0027] Sheet 10 is preferably approximately {fraction (3/32)} of an inchthick, which is somewhat thicker than standard veneers, which commonlyrun {fraction (1/32)} of an inch. This additional thickness isbeneficial in that it permits the veneered article to be milled afterapplication of the veneer to result is a smooth, flat, high-qualitysurface. With thinner veneers, any surfacing after application of theveneer carries with it a substantial risk of cutting through the veneerand exposing the underlying core in places.

[0028] It is important to note that part of the function of the hingestructure is to pull the interior sides of the groove together to insurea tightly closed joint and intimate contact between the sides. This isimportant because, while the thin layer of wood may cover the joint whenthe veneer is first applied, the subsequent milling or surfacing of theveneer will generally expose the joint. Therefore, the joint should beas tight as possible to maintain the best possible appearance.

[0029] In contrast to existing veneering techniques, which typicallyonly apply veneer to one or at most two opposite sides of a core at atime, the present invention involves application of veneer to at leasttwo adjacent sides simultaneously. As a result, existing presses havenot been suitable for use with the present invention because they arenot designed to supply heat or sufficient pressure simultaneously to twoadjacent sides. Of course, it is possible to prepare a veneered article,as shown in FIG. 3, simply using clamps and a standard wood glue.However, a press is preferred because of the higher output attainablethrough automation.

[0030] A press constructed according to the present invention andconfigured to supply heat and sufficient pressure to adjacent sides of aveneered core is shown at 100 in FIG. 4. Press 100 includes a frame 102which supports a fixed lower platen assembly 104, a moveable upperplaten assembly 106, a fixed side platen assembly 108 and a moveableside platen assembly 110. The platen assemblies are configured to clampa press charge 112 from the sides and top and bottom simultaneously, asshown in FIG. 5.

[0031] As also shown in FIG. 5, lower platen assembly 104 includes anelongate tube-like support frame 114 which runs the length of the frame.The support frame includes strength tubes 115 disposed periodicallyalong its length to increase rigidity. A three-eighths-inch thick steelsupport plate 116 rests on top of the support frame and carries a thick,ultra-high molecular weight polyethylene (UHMWPE) dielectric layer 118.Steel tabs 120 are placed periodically along the length of the supportframe to prevent lateral shifting of the support plate and dielectriclayer.

[0032] Dielectric layer 118 includes an upper slot 122 configured toreceive a key 124 formed on the bottom of a lower electrode 126. The keykeeps the electrode from shifting from side-to-side relative to thedielectric layer when the press is operated. The electrode isapproximately ½ inch thick, 10 inches wide and is preferably made ofaluminum. A pair of flat-head nylon bolts 128 are located every fivefeet along the length of the platen to further help hold the electrode,dielectric layer, support plate and support frame together. Thedielectric layer serves to electrically isolate the electrode.

[0033] A conveyor belt 130 fits on top of electrode 126 to convey thepress charge. The conveyor belt also electrically insulates the presscharge from the electrode. The belt includes a downwardly projectingguide portion 132 at either edge to help guide the belt track over theelectrode. The belt includes a return section 134 that passes backthrough the inside of support frame 114. As shown in FIG. 4, the belt isdriven by a motor 136 and rides on end rolls 138 (only one shown)mounted at either end of the support frame.

[0034] Upper platen assembly 106 is disposed in opposition over lowerplaten assembly 104 and includes a support frame 140 which is held inplace in frame 102 by a series of angle brackets 142. Each angle bracketincludes a vertical slot 144 through which a bolt passes and engages thesupport frame. The support frame is also connected to frame 102 by fourthreaded rods 146, each of which passes through a threaded brass insert148 mounted in frame 102 and is rotatably attached to the support frame.The four rods are tied together by a chain and sprocket system 150 and acrank 152 is attached to one of the rods. By turning the crank, a useris thereby able to raise and lower the upper platen to accommodate presscharges of different thicknesses.

[0035] A series of air-powered actuators 154 are attached along thebottom of support frame 140. The actuators are disposed on 12-inchcenters and each can produce up to approximately 10,000 pounds of force.Firestone Airstroke® actuators, style 19-.75 are used in the preferredembodiment.

[0036] A half-inch aluminum support plate 156 is fixed to the bottomsides of the series of actuators. A thick UHMWPE dielectric layer 158,similar to dielectric layer 118, is disposed beneath the support plateand in turn supports an upper electrode 160. The support plate,dielectric layer and electrode are held together by pairs of flat headnylon bolts 162 disposed every 24 inches along the length of the platen.

[0037] A UHMWPE slip sheet 164 fits over and around the support plate,dielectric layer and electrode to provide a replaceable protective coverfor the electrode. It is important that the cover be replaceable becausethe surface can be damaged from occasional arcing that occurs in thecourse of RF heating. The slip sheet is preferably formed from a singlepiece of UHMWPE by machining four elongate grooves, similar to thoseformed in the veneer sheet. The grooves allow the sheet to fold aroundthe support plate, dielectric layer and electrode. The sheet is held inplace by toggle clamps 166 located on the upper surface of the supportplate between the actuators.

[0038] It should be noted that the lower surface of the upper platenassembly can conform somewhat to slight thickness variations in thepress charge by virtue of the flexibility of the series of actuators.The lower platen assembly, in contrast, provides a fixed, flat referencefor the press charge.

[0039] Fixed side platen assembly 108 is carried by a beam 170 to whichis mounted a spacer 172 and a clamp 174. The clamp is configured to holda platen block 176 consisting of a UHMWPE dielectric block 177, ahalf-inch thick aluminum electrode 178 and a UHMWPE contact sheet 179.The electrode is held in place on the dielectric block by a series ofnylon bolts and the contact sheet is held to the electrode by anadhesive tape. Note that the contact sheet is shown formed with across-section to match a beveled veneered article, such a shown at 112and in FIG. 3. This is to illustrate the flexibility of the presentinvention to accommodate a non-rectangular press charge, but it isanticipated that, most commonly, a flat sheet would be used because mostproducts are rectangular in cross-section.

[0040] Moveable side platen assembly 108 is carried by a beam 180 towhich is mounted an actuator support 182. The actuator support includesa fixed portion 184 which is welded to the beam and a moveable actuatorcarrier 186 that can be adjusted up and down to maintain a series ofactuators 188 mounted thereto in vertical alignment with the presscharge. The actuators are generally similar to actuator 154 describedabove, but are somewhat smaller and referred to as style 16. As withactuators 154, actuators 188 are disposed in an essential continuousedge-to-edge series.

[0041] The side platen assembly also includes a platen block 190 whichincludes a dielectric block 192, a half-inch thick aluminum electrode194 and a UHMWPE contact sheet 196, constructed in the same fashion asplaten block 176. Platen block 190 is carried by a floating blockcarrier 198 which includes an inverted T-beam 200 which rests on beam180. A spacer 202 and a clamp 204 are mounted to beam 200 to secure theplaten block. The side of the beam opposite the platen block is disposedadjacent the actuators to receive pressure therefrom, but the beam isnot directly connected to the actuators. This allows the actuators to beadjusted vertically as needed to maintain centering on the press charge,as described above.

[0042] The platen blocks are prepared with a height configured to matchthe height of the desired press charge. Thus, when the upper platenpresses down on the press charge, there is just enough room for theplaten blocks to slide in between the upper and lower platens to applypressure to the sides of the press charge.

[0043] Although not shown, the electrodes are to be connected to one ortwo RF generators to supply heat to cure the glue in the press. It isanticipated that the upper and lower platens would be connected to an RFgenerator as a pair and then the two sides would be connected. It wouldbe possible to either switch a single generator between the upper/lowerand side platen pairs or to use a separate RF generator for each platen.It may be preferable to use two generators to overcome the difficultiesin adjusting the tuning to account for the different capacitancesbetween the two platen pairs. In either case it is believed that it ispreferable to operate the platen pairs in sequence rather thansimultaneously to thereby eliminate hot spots that might occur withsimultaneous vertical and horizontal glue line heating. It will beunderstood by those of skill in the art that the upper and lower platensprimarily heat the vertically-oriented glue lines when activated and theside platens heat the horizontally-oriented glue lines. It should alsobe noted that it is anticipated that the inactive pair of platens wouldbe floating relative to ground during the operation of the other pair ofplatens.

[0044] It should be noted that the above-described press is a batchpress and the conveyor is simply used to carry products into and out ofthe press. In the preferred embodiment, the press has a length ofapproximately 24 feet. This is much longer than required for mostindividual pieces, but allows for multiple pieces to be placedend-to-end. In addition, the press has a pressing cross-section 6 incheshigh by 10 inches wide. This allows multiple pieces to be stackedside-by-side for simultaneous curing to thereby increase the output ofthe press.

[0045] In operation, an operator will first prepare veneer sheets asdesired for application to cores. Glue is applied to the veneer sheetsand the operator then wraps the sheets around the cores and feedsunbound article into the press. After filling the press with the desirednumber of pieces, the press is closed, pressure is applied to the piecesand one opposed set of platens is energized with RF energy to cure anyglue lines extending between the energized platens. After the first setof glue lines has been cured, the other set of opposed platens inenergized to cure the remaining glue lines. The cure parts are then fedout of the press to be further processed.

[0046] As mentioned above, after gluing, the parts are surfaced toprovide a high quality final surface. Surfacing will typically removeapproximately half of the thickness of veneers such as shown in FIG. 1.Because the veneer starts out rather thick, enough material is left inthe layer of veneer so that cutting through the veneer is not asubstantial problem. Once surfaced, the veneered articles are ready forincorporation in a final product, such as in an extension jamb 206 for awindow, as shown in FIG. 6. Of course, veneered products or articlesprepared according to the present invention could be used in manydifferent applications where a high quality wood surface is desired.

[0047] Although the present invention has been described with respect toveneering all four sides of a core, in many applications it is onlynecessary to apply the veneer to two or three sides of a core. In such acase the veneer sheet would be prepared accordingly with only one or twogrooves, as necessary. The pressing and finishing operations wouldremain as previously described. In some cases it may also be desirableto veneer three sides of a core and laminate an edge band onto thefourth side. For instance, it may be desirable to form door stiles inthis fashion, with the edge banding providing material in which to milla molding profile.

[0048] One of the benefits of the press constructed according to thepresent invention is that it can cure glue lines on all four sides of anarticle in a single pass. This is not limited to the case where veneeris applied to all four sides, but could also be used with theabove-described door stile construction. Moreover, in some cases it maybe desirable to provide multiple layers of material in certain areas ofa product. The described press can process virtually an unlimitedvariety of core/laminate/veneer/edging combinations.

[0049] While the invention has been disclosed in its preferred form, itis to be understood that the specific embodiment thereof as disclosedand illustrated herein is not to be considered in a limited sense andchanges or modifications may be made thereto without departing from thespirit of the invention.

I claim:
 1. A press assembly comprising: a first moveable platen memberand associated first drive mechanism that moves the first moveableplaten member in a first direction toward a first fixed platen member, asecond moveable platen member and associated second drive mechanism thatmoves the second platen member in a second direction toward a secondfixed platen member, and a control mechanism that actuates the first andsecond drive mechanisms to press simultaneously the first and secondplaten members towards the first and second fixed platen members,respectively.
 2. The press assembly of claim 1 , wherein the firstdirection is substantially perpendicular to the second direction.
 3. Thepress assembly of claim 1 , wherein the drive mechanisms cause each ofthe first and second platens to apply a force of at least about 10,000pounds.
 4. The press assembly of claim 1 , wherein the drive mechanismsinclude air-powered actuators.
 5. A press assembly for pressing anarticle having a top, bottom and two sides, comprising a frame, a platenassembly connected to the frame configured to clamp the article from thesides and top and bottom simultaneously.
 6. The press assembly of claim5 further comprising a heating device configured to apply heat toadjacent sides of the article.
 7. The press assembly of claim 5 ,wherein the platen assembly includes moveable platens driven byair-powered actuators toward fixed platens.
 8. A method of forming awood product comprising providing a core having first and secondadjacent sides, applying a first sheet to the first side of the core,and a second sheet to the second side of the core, placing the core andthe sheets into a press having a first platen that is moveable in adirection perpendicular to the first side of the core, and a secondplaten that is moveable in a direction perpendicular to the second sideof the core, and actuating the first and second platens to press thefirst and second sheets against the first and second sides of the coresimultaneously.
 9. The method of claim 8 further comprising applyingglue between the sheets and the core before the placing step.
 10. Themethod of claim 8 , wherein each sheet comprises veneer.
 11. The methodof claim 9 , wherein the glue comprises a thermosetting resin.
 12. Themethod of claim 8 , wherein the first and second sheets are connected bya hinge structure.
 13. The method of claim 8 , wherein the firstdirection is substantially perpendicular to the second direction. 14.The method of claim 8 , wherein each of the first and second platensapplies at least approximately 10,000 pounds of pressure.
 15. The methodof claim 8 , wherein the actuating step is carried out by air-poweredactuators.